So. Usually I just pay a guy to do this kind of stuff but I'm wanting to get better at DIY. So even though I've been playing a long time, I"m a rookie on this front. My Fender '65 Princeton Reverb RI has started to crackle when it's turned up or there's any gain. I'm assuming this is a tube issue. My questions are: -Is that a reasonable assumption? -What is rebiasing? -If I just stick the same tubes in, does rebiasing even affect me? Thanks.